A343264 - cp's OEIS frontend

A343264 Cardinalities of the sets of fusible numbers obtained at the consecutive steps of their construction as follows. We set S(0) = {0}. S(n+1) is obtained by adding to S(n) the sums (x+y+1)/2 for all x,y from S(n) with the property |x-y| < 1. Then, a(n) is the number of elements in S(n).

n	a(n)
0	1
1	2
2	4
3	9
4	21
5	50
6	119
7	281
8	656
9	1513
10	3449
11	7777
12	17363
13	38422
14	84355
15	183915
16	398526
17	858901

[1, 2, 4, 9, 21, 50, 119, 281, 656, 1513, 3449, 7777, 17363, 38422, 84355, 183915, 398526, 858901]